1. Field of the Invention
This invention relates to an improved tennis racket with a split frame and, more particularly, to a tennis racket frame formed of a pair of tubes attached together in the bow area and then separated in the throat-beams.
2. Summary of the Background Art
Modern tennis rackets are normally formed of a tube of moldable material. The tube is first bent internally concave in the plane of the strings into a shape with a bow extending from the tip at the top, then bent at an intermediate portion to extend to Y-shaped throat-beams, straight or curved, and then bent convexly extending in parallel handles to the but end at the bottom. A yoke piece is formed into the frame at the bow adjacent to the throat-beams. The yoke and bow portions of the frame form an oval with strings located thereacross to constitute a planar ball-striking surface.
Due to the construction of the frame, when a ball is struck by the strings of the racket, the strings and frame are bent rearwardly by the force of the ball. This causes those portions of the frame on the side remote from the ball to bend in a concave configuration generating compressive forces in the frame. At the same time, the portions of the frame on the same side as the ball generate tension forces in the frame. The combination of compression and tension forces on various portions of the frame will create a detrimental pattern of forces, including shear forces between the tension and compression forces, reducing the efficiency and life of the frame and racket.
In addition, there has been a recent effort to design tennis rackets with increased frequency. A typical design would enlarge the frame in a direction perpendicular to the strings at about the mid-point of the height of the racket between the tip and butt ends. When such frame construction is utilized, it is normally characterized by the stretching of the frame material during fabrication. When stretched, the walls of the frame become increasingly thinner and lighter weight. Strength is maintained by wrapping additional materials thereover during fabrication.
Lastly, the exterior periphery of the frame around the bow is normally provided with a grommet strip. Such grommet strip is actually a pair of strips, one over the upper portion of the bow extending symmetrically from the tip. The other grommet strip is on the exterior periphery of the yoke between the throat-beams. The construction of such conventional bows causes an inconvenience of installing grommet strips of plural parts for one function during construction and repair. Such grommet strip construction is discontinuous, separated at regions of the bow where it couples to the throat-beams whereat strings may not pass through the bow.
Various approaches are disclosed in the patent literature for improving tennis rackets, particularly tennis racket frames. Note, for example, U.S. Pat. Nos. 4,664,380 and 4,768,786 to Kuebler. Those patents teach enlarging the frame at about the mid-point of their height. Other portions of the frame remote from the handle may also be enlarged. Such enlargement is for increasing frame frequency. Using conventional fabrication techniques, the reduced thickness of the frame walls of such tennis rackets, unless bolstered by additional material provided during fabrication, will reduce strength. A similar design is commercially sold by the Wilson Corporation under the designation of PROFILE, a wide body tennis racket. The present invention attains increased stiffness through two separate beam tubes which are split at regions in the head resulting in reduced materials, weight and cost since there is no material between the tubes at the region of the split beams.
In addition, U.S. Pat. No. 1,539,019 to Nikonow teaches the use of thick frames. The Nikonow frame, however, is constructed of wood and does not address the fabrication problems of modern molded tennis rackets. In another patent, U.S. Pat. No. 4,913,434 to Fischer, a frame is made up of a pair of tubes. Such frame, however, separates the two tubes by an intermediate layer thereby complicating fabrication and incurring increased costs. Further, the tubes remain in such relationship throughout their entire extent and are not provided with openings in the throat-beams to facilitate the use of a one piece grommet strip. Lastly, U.S. Pat. No. 4,293,129 to Planakis discloses a tennis racket frame formed of two tubes. Such racket has two sets of strings, one on each tube in non-parallel planes.
As illustrated by the great number of prior patents and commercial devices and techniques, efforts are continuously being expended in an effort to improve tennis rackets and their frames. Such efforts are being made to render such frames more efficient, reliable, inexpensive and convenient to manufacture and use. None of these previous efforts, however, provides the benefits attendant with the present invention. Additionally, the prior patents and commercial devices and techniques do not suggest the present inventive combination of component elements arranged and configured as disclosed and claimed herein.
The present invention achieves its intended purposes, objects and advantages through an unobvious combination of component elements, with the use of a minimum number of parts, at a reasonable cost to manufacture and by employing only readily available materials.
Accordingly, it is an object of the present invention to provide an improved tennis racket comprising a frame formed of a pair of tubes extending from their mid points at the tip end in symmetric curves to form the majority of the string-supporting bow, then towards each other in an essentially V-shaped configuration to form the throat-beams, and then in a parallel configuration to form the handle and then terminating at the butt end, the tubes being attached together throughout the majority of the bow and then separated in the throat-beams for at least a portion of their extents; a yoke attached to the tubes adjacent to the ends of the throat-beams remote from the butt end to form, in association with the portions of the tubes between the throat-beams and the tip, an essentially oval-shaped bow, the periphery of the bow having spaced holes therethrough; a single groove formed around the entire external periphery of the bow; a continuous grommet strip positioned within the groove and extending through the openings in the throat-beams and around the entire external periphery of the bow, the grommet strip being provided with spaced holes aligned with the holes of the bow; a bumper strip positioned under a portion of the grommet strip including the tip, the bumper strip being provided with spaced holes aligned with the holes of both the bow and the grommet strip, the holes of the bumper strip, grommet strip and bow being perpendicular to the tangent of the inner head arc and outer head arc of the frame; strings extending through the holes of the bumper strip, grommet strip and bow to form a planar ball-striking surface across the bow; a pallet surrounding the frame at the handle; and a grip surrounding the pallet at the handle for being grasped by a player.
It is a further object of the present invention to separate the compression and tension forces, and to abate the stress forces therebetween which are normally imparted to a tennis racket frame upon the striking of balls.
It is a further object of the invention to configure two tubes into a tennis racket frame in a particular configuration so as to "engineer-in" the desired playing characteristics.
It is a further object of the present invention to form openings in the frame of a tennis racket in the throat-beam area.
It is a further object of the present invention to utilize a continuous grommet strip around the entire periphery of the frame.
It is a further object of the invention to form all the holes of the bumper strip, grommet strip and bow perpendicular to the tangent of the frame, at right angles to both the internal head arc and the external head arc.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.